The chloride ion is the most abundant anion in the extracellular fluid with approximately 88% of chloride found in extracellular fluid and just 12% intracellular.
Chlorides in blood easily transfer between the blood fluid and erythrocytes in what is commonly known as the chloride shift or Hamburger phenomenon, a primary homeostatic mechanism for the control of blood pH.
In chloride shift the carbonate ion diffuses out of red blood cells (RBCs) into the plasma, the inside of the cells become less negatively charged.
The deficit of negative ions within the RBC is countered by the inward influx of chloride ion, thus maintaining electrical balance of the RBC in the face so a large carbonate ions efflux.
The movement of chloride ions into RBC is called chloride shift and this process is mediated by Band 3, a major ion exchange membrane protein.
It has a half-time in human blood at 37 ° C of ~100 ms, allowing for almost all of the chloride shift to occur during the transit time within the capillary.
The process requires a protein transporter that moves chloride ions and bicarbonate ions in opposite directions across the cell membrane.
Phenomenon of chloride shift
